Acetic anhydride modified disproportionated rosin

ABSTRACT

IN SYNTHETIC RUBBER MANUFACTURING PROCESSES WHEREIN AQUEOUS EMULSIONS OF BUTADIENE AND STYRENE OR BUTADIENE AND ACRYLONITRILE OR OTHER VINYL MONOMERS ARE PREPARED WITH AN EMULSIFYING AGENT CONTAINING A WATER-SOLUBLE SOAP OF A DISPROPORTIONATED ROSIN AND ARE POLYMERIZED IN THE PRESENCE OF A FREE RADICAL CATALYST SYSTEM, THE ADVERSE ACTION OF FREE OXYGEN ON THE POLYMERIZATION IS OFFSET BY HEAT-MODIFYING THE DISPROPORTIONATED ROSIN BEFORE IT IS CONVERTED INTO ITS SOAP. THIS IS DONE BY HEATING IT AT ABOUT 250*-300*C. FOR ABOUT 1 TO 4 HOURS IN ADMIXTURE WITH ABOUT 0.5% TO 5% OF ITS WEIGHT OF ACETIC ANHYDRIDE.

United States Patent Office 3,700,634 Patented Oct. 24, 1972 3,700,634ACETIC ANHYDRIDE MODIFIED DISPROPORTIONATED ROSIN Charles Glenn Wheelus,Panama City, Fla., assignor to Arizona Chemical Company, New York, N.Y.No Drawing. Original application Nov. 27, 1968, Ser. No. 779,600, nowPatent No. 3,583,934, dated June 8, 1971. Divided and this applicationApr. 24, 1970, Ser.

Int. Cl. C09f 1/04 U.S. Cl. 260-975 2 Claims ABSTRACT OF THE DISCLOSUREIn synthetic rubber manufacturing processes wherein aqueous emulsions ofbutadiene and styrene or butadiene and acrylonitrile or other vinylmonomer are prepared with an emulsifying agent containing awater-soluble soap of a disproportionated rosin and are polymerized inthe presence of a free radical catalyst system, the adverse action offree oxygen on the polymerization is offset by heat-modifying thedisproportionated rosin before it is converted into its soap. This isdone by heating it at about 250-300 C. for about 1 to 4 hours inadmixture with about 0.5% to 5% of its weight of acetic anhydride.

This is a division of application Ser. No. 779,600, filed Nov. 27, 1968.This invention relates to emulsion polymerization processes, such asthose used in the manufacture of synthetic rubbers, wherein aqueousemulsions of a diolefin such as butadiene and a vinyl monomer such asstyrene or acrylonitrile are prepared and the unsaturated monomers arecopolymerized in the presence of a free radical catalyst system. Moreparticularly, the invention is directed to improvements in theseprocesses wherein the adverse effect of free oxygen on thecopolymerization reaction is offset or counteracted by the use of a newclass of disproportionated rosin soaps in preparing the monomeremulsions.

In synthetic rubber manufacturing processes of this type, andparticularly in the manufacture of GRS- and nitrile rubbers, the alkalimetal and other water-soluble soaps of disproportionated rosin arecommonly used as emulsifying agents, either alone or admixed with fattyacid soaps. Standard recipes employing these and other similaremulsifying agents are described, for example, in Whitby, SyntheticRubber (1954 edition) Page 217. A typical GRS formulation that is usedboth commercially and in the laboratory is the 1500-type SBR recipe.Other recipes for use in nitrile rubber formulations, in GRS latexes ofeither high or low solids, and other processes wherein diolefins such asbutadiene or mixtures thereof with styrene, acrylonitrile, alkylacrylates, 2-vinylpyridine and the like are emulsified in aqueoussystems and polymerized with free radical catalysts are also describedin this book.

The polymerization catalysts and catalyst systems used in these emulsionpolymerizations are also described in the Whitby book. They includepersulfate catalysts such as potassium persulfate, peroxide catalystssuch as cumene hydroperoxide, hydrogen peroxide and the like, and redoxsystems such as those in which ferrous sulfate and sodium formaldehydesulfoxylate are used with para-menthane hydroperoxide. Modifiers such asdodecyl mercaptan and electrolytes such as sodium phosphates andpotassium chloride may also be present.

'Emulsion polymerization processes of these types are seldom carried tocompletion. Ordinarily the polymerization is so conducted that about 60%to 70% of the monomers are polymerized, after which it is short-stoppedand the reactor is discharged and refilled with fresh emulsion. Underthese circumstances it is difficult or impossible to prevent smallamounts of oxygen from finding its way into the reactor and in manycases, therefore, the polymerization must be carried out in the presenceof oxygen. This is very undesirable, as free oxygen lengthens theinduction period of most of the above-described polymerization systemsand may seriously reduce the daily output of the plant.

My present invention is based on the discovery that this adverse effectof oxygen can be oflset or overcome to a substantial extent by thepresence in the polymerization system of a new class ofdisproportionated rosin soaps. These are the alkali metal, ammonium andamine salts of disproportionated rosin that has been modified by mixingit with about 0.5% to 5% of acetic anhydride and heating the mixture atabout 250 C. to 300 C. or slightly higher for about 1 to 4 hours. Aceticanhydridemodified rosin of this character is a new article of commerce,and will be sold as such to synthetic rubber manufacturers forconversion into the water-soluble soaps that are used as emulsifyingagents in preparing synthetic rubber-producing compositions. The soapsof the acetic anhydride-modified disproportionated rosin with alkalimetal hydroxides or carbonates, or with ammonia or amines such asmorpholine are also new products, and are claimed as such.

This aspect of my invention therefore includes the new aceticanhydride-modified disproportionated rosin, its water-soluble soaps,aqueous butadiene-styrene and other synthetic rubber-producing emulsionscontaining the new soaps as emulsifying agents, and methods of producingsynthetic rubbers in which these emulsions are polymerized.

In my copending application Ser. No. 692,713, filed Dec. 22, 1967 nowabandoned, I have shown that disproportionated rosins can beheat-modified by holding them at about 250 to 300 C. for about 1 to 18hours and that the water-soluble soaps of such heat-modified rosins,when incorporated into aqueous butadiene-styrene emulsions in the usualquantities of about 1% to 8% on the Weight of solids present, willcounteract the adverse eifect of oxygen on their copolymerization intosynthetic rubber. The emulsions containing these soaps also polymerizefaster than those prepared with other emulsifying agents undercomparable polymerizing conditions in the absence of oxygen. I have nowdiscovered that these same advantages are obtained when the samedisproportionated rosins are heat-treated for much shorter times afteradmixture with about 0.5 to 5% of their weight of acetic anhydride.

Although my invention is not limited to any theory of operation, Ibelieve that the acetic anhydride accelerates the formation ofanhydrides of the rosin acids contained in disproportionated rosins(see, for example, U.S. Pat. No. 2,138,183). I have shown that suchanhydrides are present by the following procedures. A sample of adisproportionated rosin, heat modified by incorporating uniformly 1% byweight of acetic anhydride and heating for 2 hours at 300 C., isconverted into its potassium soap by reaction with aqueous potassiumhydroxide. A weighed portion of this soap is acidified with mineral acidto free its organic acids which are extracted with ether and washed withwater to remove mineral acids and acetic acid. The acid number of theextracted acids is determined and compared with the acid number of thetreated rosin.

The acid number of the treated rosin is always lower by at least 1% to5%, and in many cases it may be as much as 20-25% lower; typical figureswill be shown later in Table I. The process of my present invention cantherefore be defined accurately by stating that the disproportionatedrosin is heated at 250 C. to 300 C. and preferably about 290300 C. inthe presence of about 0.5% to 5% and preferably about 1% to 4% of itsweight of acetic anhydride, uniformly admixed therewith, until asubstantial rosin acid anhydride formation has occurred. For mostdisproportionated rosins this result is obtained in from 1 hour to about4 hours under these conditions. A heating schedule of about 2 hours at290300 C. or slightly higher after adding 1% to 2% of acetic anhydrideis preferred.

A particularly important feature of my invention is the application ofits principles to tall oil rosin. Soaps of disproportionated tall oilrosin are used commercially in synthetic rubber recipes, such as thosefor GRS- rubbers, with results that are about the same as those obtainedwith disproportionated wood rosin. I have found, however, thatoutstanding results are obtained when disproportionated tall oil rosinsare heat-modified in accordance with my present invention and thenconverted into water-soluble soaps; these soaps give greatly improvedpolymerization rates when used as emulsifiers in free radical typeemulsion polymerization recipes. Thus, for example, the presence ofabout 1% to 8% of the potassium soap of one of the new disproportionatedrosins, modified by heating with acetic anhydride, in styrene-butadieneemulsion polymerization systems will result in from 20% to 30%reductions in the time required to reach 6070% conver- -sion at 5 C.

The disproportionated rosin used as starting material in practicing theinvention is a rosin wherein two atoms of hydrogen have been removedfrom the two-double bond abietic-type acids with rearrangement to forman aromatic nucleus; as used herein it is a rosin wherein the abieticacid content has been reduced by this procedure to less than fivepercent and preferably to not more than about 1%. This is donecommercially by heating the rosin in the presence of adisproportionation catalyst such as iodine, sulfur, or palladium orplatinum as described in U.S. Pat. No. 2,138,183. See also US. Pat. No.2,479,226, wherein the disproportionation reaction is applied to talloil and alkali metal salts of the product are used in butadienestyrenepolymerizations.

In producing my new heat-modified rosins the disproportionated rosin isheat-modified in the presence of acetic anhydride as described aboveuntil the product, after conversion into its sodium, potassium or otheralkali metal soap, demonstrates a faster conversion of butadiene-styreneemulsion into synthetic rubber when tested in a standard SBR recipe incomparison with a soap of the same rosin before the modification. Ameasurable improvement is obtained after heating with 1% to 4% of aceticanhydride for one hour at 250-270 C., but it is advisable to continueheating for from 2 to 4 hours. At higher temperatures, however, andespecially in the range of about 290 C.-300 C. the modification proceedsmuch more rapidly and the desired improvement is obtainable inconsiderably less time. Heating temperatures up to 325 C. may be usedfor short times on the order of 0.5-2 hours, but care must be taken toavoid excessive decarboxylation of the rosin.

The heat-modified rosins resulting from this process are new articles ofcommerce and will be sold as such to synthetic rubber manufacturers forconversion into their alkali metal, ammonium or amine soaps such as thesodium, potassium and morpholine salts. These may be prepared separatelyby reacting the rosin with aqueous solutions of hydroxides or carbonatesof the alkali metal, or with ammonium hydroxide, or with a volatileamine such as morpholine, or the soap may be formed in situ by addingits ingredients to the polymerization recipe.

The reasons why soaps of the new heat-modified disproportionated rosinsgive improved conversions in the emulsion polymerization of olefins andpolyolefins have not been definitely determined. It seems likely thatthey produce soap micelles of more favorable character, for it isgenerally agreed that these polymerizations are initiated in suchmicelles. Rosins, being natural products, may contain substances whichact as inhibitors in the polymerization reaction. These compounds may bealtered by the heat-treating conditions in sucha manner that they nolonger act as inhibitors. It will be understood, however, that theinvention is not primarily dependent on these or other theoreticalpossibilities, the controlling fact being that improved conversions areobtained when the soaps of heat-modified disproportionated rosin areused in olefin polymerizations.

It will also be understood that the decreased time of polymerization isobtainable in any aqueous emulsion polymerization system in which rosinsoaps are used. Thus, in addition to GRS rubber, the new soaps may beused in nitrile rubber formulations, in GRS latexes of either high orlow solids, and in general wherever polyolefins such as butadiene ormixtures thereof with styrene, acrylonitrile, alkyl acrylates,2-vinylpyridine and the like are polymerized in aqueous systems, usuallyat temperatures ranging from about 4 C. to about 50-60 C. It will alsobe understood that they may be used with any of the catalyst systemsnormally employed in these polymerizations. It will be seen therefore,that the new soaps of the invention may be used in any of thepresentlyknown emulsified olefin polymerization systems.

A standard type of formulation in wide commercial use for the productionof cold rubber is the sulfoxylate recipe, in which the activatorcontains sodium formaldehyde sulfoxylate, ferrous sulfate and VerseneFe-3 or other chelating agent. See Whitby, Synthetic Rubber (1954edition), page 217. A typical GRS formulation that is used bothcommercially and in the laboratory is the 1500- type SBR recipe. Whenused for test purposes this is as follows:

Laboratory 1500 Recipe The following components are charged to a32-ounce bottle and polymerization is allowed to take place for 8 hoursat 5 C.

.610. 0.025 g., tetra sodium salt of EDTA (ehelating agent 5.-

ethylene-diamine tetracetic acid basis. Tertiary dodecyl mercaptan.0.310 g. 100% basis. p-Menthane hydroperoxide 0.038-0046 g., 100% basis.Sodium formaldehyde sulioxylate. 0036-0043 g. Ferrous sulfate 0.0130.015g.

1 Tamol N is a salt of a naphthalene sultonate-tormaldehyde condensateOxygen is a known inhibitor in the polymerization of styrene-butadiene.Since it is diflicult to remove all traces of oxygen from a commercialpolymerization system, air is sometimes deliberately introduced into theexperimental system at the rate of 4 ml. per 100 g. monomer to determineits effect on the polymerization. This is equivalent to 6.2 ml. in therecipe outlined above. This was done in all of the present examplesexcept where otherwise stated.

The charging procedure is as follows: The potassium soap ofdisproportionated rosin, Tamol N, and KCL are dissolved in 200 g.distilled water and adjusted with 2 N KOH to a pH of 10.5. Thissolution, along with 75 ml. additional distilled water, is charged to abottle previously sparged with nitrogen. Styrene, less an amount used todissolve the para-menthane hydroperoxide and tertiary dodecyl mercaptan,is added to the bottle. The tertiary dodecyl mercaptan and para-menthanehydroperoxide separately dissolved in styrene are added next to thebottle. A slight excess of butadiene is weighed into the bottle, theexcess allowed to evaporate, and the bottle quickly capped with a metalcap and neoprene seal. The cap has a small hole so that solutions may beadded and samples removed through the neoprene seal by use of ahypodermic syringe.

The sodium formaldehyde sulfoxylate, sodium TDTA, and ferrous sulfateare dissolved in water under a nitrogen blanket. The bottles are placedin racks in a polymerization apparatus which is maintained at 5 C. Thebottles are rotated until the contents are thoroughly emulsified andchilled. An appropriate amount of the ferrous sulfate, sodiumformaldehyde sulfoxylate, and sodium EDTA solution is charged to eachbottle and the bottles are rotated 8 hours after which the reaction isshort-stopped.

After reaction times of 8 hours the amount of solids is determined. Thepercent conversion of monomer to polymer is calculated from this figure.

Alkali me'tal soaps of the heat-modified disproportionated tall oilrosins of the invention can also be used as emulsifying agents in makingnitrile rubber. Thus, for example, they can be substituted for the soapflakes in the recipe shown on page 802 of the Whitby publication citedabove.

The invention will be further described and illustraeed by the followingexamples, which described specific embodiments thereof. It will beunderstood, however, that although these examples may show certainfeatures in detail, the invention in its broader aspects is not limitedthereto.

The rosin used in Example I was a catalytically produceddisproportionated tall oil rosin, prepared as described in US. Pat. No.2,138,183 and having the following characteristics:

Acid number 167 Saponification number 173 Unsaponifiables, percent 7.0Abietic acid (U.V.), percent 0.7 Optical rotation +32 Softening point,C.

Acid number 157 Unsaponifiables, percent 9 Abietic acid, percent 0.02Optical rotation +48 Softening point, C. 65

EXAMPLE 1 A sample of the rosin weighing 400 grams was charged to a1-liter, 3-necked flask to which was attached an agitator, a gas inlettube for nitrogen gas, a reflux condenser, and an addition funnel withan inlet tube extending under the surface of the rosin. Heat was appliedand the rosin temperature was raised to 300 C. under a blanket ofnitrogen. At 300 C., 4 grams of acetic anhydride, dissolved in a littleheptane, was added slowly and with agitation. The contents of the flaskwere then heated at 300 C. for 2 hours while the agitation wascontinued.

reaction with aqueous potassium hydroxide, and the soap was used as theemulsifying agent in the laboratory 1500 recipe in comparison with asoap of the same rosin that had not been heat-modified.

Eight polymerization bottles were prepared, four for each soap. Afterall components of the receipe were charged air was added to two of thebottles of each set in the amount of 4 ml. for each grams of butadieneand styrene monomer and polymerization was carried out by shaking thebottles at 5 C. for 8 hours. The following results are in each case theaverage of two bottles.

PERCENT CONVERSION, MONOMERS TO POLYMER No air 6.2 m1. air

Control 55. 1 28. 4 Acetic anhydride, modified 59. 3 53. 1

Heating temp. C.: to Polymer None (control) 11 250 28 275 33 300 41EXAMPLE 2 A 415 gram sample of the disproportionated rosin was heatedfor 1 hour at 300 C. in the equipment described in Example 1 afteradding 8.3 grams of acetic anhydride. The treated rosin was convertedinto potassium soap which was tested in the 15 recipe, with and withoutaddition of air, by the procedure described above. The results were asfollows:

PERCENT CONVERSION, MONOMERS TO POLYMER N 0 air 6.2 ml. air

EXAMPLES 3-6 The procedure of Example 2 was repeated, using the samerosin and 16.6 grams (4 percent) of acetic anhydride, a two-hour heatingperiod, and temperatures of 250 and 300 C. Control runs were also madein which smaller proportions of acetic anhydride, or none at all, wereused. In all cases the treated rosins were made into potassium soaps andtested in the 1500 recipe.

In Examples 5 and 6 a portion of the soap was acidified withhydrochloric acid and the liberated organic acids were extracted withether and washed with water. Their acid number was then determined, andis tabulated below under the heading extracted acids.

The conditions used and results obtained were as fol- The treated rosinwas made into its potassium soap by 0 lows:

TABLE I Percent conversion Conditions to polymer Acid number PercentTime, Temp., acetic 2 ml Treated Extracted Ex. hrs. C. anhydride No airair rosin acids 3 2 300 None 36. 0

4 2 300 None 52. 9 35. 1 2 300 4 55.7 50.2

7 EXAMPLES 7-8 TABLE II Wood rosin Gum rosin 6.2 ml. 6.2 ml. Percentacetic anhydride No air air No air air What I claim is:

1. An improved disproportionated rosin comprising a heat modifieddisproportionated rosin which has been heat treated at about 250 to 300C. for about 1 to 4 hours in admixture with about 0.5% to 5% of itsweight of acetic anhydride.

2. An improved disproportionated rosin soap selected from the groupconsisting of alkali metal, ammonium, and water soluble amine salts ofthe disproportionated rosin of claim 1.

References Cited UNITED STATES PATENTS 3,377,334 4/1968 McBride 260-9753,528,959 9/1970 Patrick 26097.5 2,617,792 11/1952 Floyd 26097.52,451,173 10/1948 Richter 260-975 3,518,214 6/1970 Wheelus 26097.5

DONALD E. CZAJA, Primary Examiner W. E. PARKER, Assistant Examiner US.Cl. X.R. 260102

